Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$230.44	6.840%	$246.2021	$246.20	$246.20	$246.20
Purchase #2	$40.39	9.771%	$44.3365	$44.34	$44.35	$44.30
Purchase #3	$191.88	4.681%	$200.8619	$200.86	$200.85	$200.90
Purchase #4	$203.90	12.383%	$229.1489	$229.15	$229.15	$229.10
Purchase #5	$49.56	10.106%	$54.5685	$54.57	$54.55	$54.60
Purchase #6	$106.90	4.446%	$111.6528	$111.65	$111.65	$111.70
Purchase #7	$196.80	10.599%	$217.6588	$217.66	$217.65	$217.70
7 purchase totals =	$1,019.87		$1,104.4295	$1,104.43	$1,104.40	$1,104.50